The invention relates to a balance with a weighing cell including a vertically movable load receiver, with a weighing pan to receive the weighing load, and with a support element to couple the weighing pan to the vertically movable load receiver of the weighing cell, wherein a cantilever support with a seat for at least one calibration weight of a calibration device is solidly connected to the support element.
Balances in which a cantilever element is connected to the weighing cell and in which a weighing pan and/or a calibration device is arranged at the opposite end of the cantilever from the connection to the weighing cell belong to the known state of the art. Balances of this kind are prone to the risk that the forces acting on the cantilever element may cause a deformation of the vertically movable load receiver which, in turn, may introduce harmful torques into the weighing cell, specifically into the sensitive flexure pivots of the weighing cell. This danger is present in particular when a load is placed at an off-center position on the weighing pan. In the terminology of weighing instruments, the balance has an unfavorable cornerload behavior.
A balance is disclosed in DE 33 30 988 A1, where the cantilever element receiving the weighing pan is configured L-shaped. The weighing pan is solidly connected to and supported by the free end of the horizontal leg of the L. The vertical part of the L is connected to the weighing cell by way of a U-shaped arrangement of support arms. The two horizontal pairs of arms embrace the vertically movable load receiver of the weighing cell at upper and lower locations in the planes of the parallelogram guides of the weighing cell. The arrangement of support arms is attached to the load-introduction part of the weighing cell at two support locations that are disposed vertically above each other, at the upper location with a screw connection and at the lower location by a type of attachment that allows rotation about a vertical axis within the range of elastic twisting of the arrangement of support arms. This configuration offers the possibility of a horizontal as well as vertical position adjustment of the weighing pan. Due to the fact that the force introduction occurs in the plane of the guide members, it was possible to reduce the cornerload sensitivity of the balance with this design arrangement. As a part of an overload safety device against excessive loads, a leaf spring is installed between a horizontal tilt axle that is connected to the vertical L-part of the cantilever element and the vertical section of the U-shaped support-arm arrangement, with the free ends of the leaf spring being elastically biased against the support-arm arrangement. In the normal load range, the leaf spring behaves as a quasi-rigid abutment. In the overload range, it allows the horizontal arm of the L-shaped cantilever element to yield flexibly within a limited range.
While the U-shaped support-arm arrangement described in DE 33 30 988 A1 is elastic with regard to twisting, it still has a fixed connection to the weighing cell through the screws. This creates the danger that deformations of the U-shaped support-arm arrangement are still introduced, albeit in attenuated form, directly into the load-receiving area of the weighing cell where they have an effect on the flexure joints. Furthermore, the force that triggers the overload safety device is position-dependent. This means that the nearer the point of force application is to the support-arm arrangement, the stronger the force has to be to release the overload safety device. Furthermore, the balance disclosed in DE-33 30 988 A1 offers no solution for the protection of the sensitive flexure pivots of the weighing cell against excessive vertical forces applied in the reverse direction to the force caused by a weighing load. Forces of this kind can occur, e.g., if the balance is abruptly put upside down during transportation of the balance in its shipping container such that the balance is standing on its head, so to speak, especially if the balance is exposed to an abrupt deceleration in the process.